Q about VSZ wrt NPTL

From: Sameer Suhas Deokule <sdeokulecluster yahoo com>

To: phil-list redhat com

Subject: Q about VSZ wrt NPTL

Date: Tue, 27 Apr 2004 14:27:16 -0700 (PDT)

Where can I find more info about the following ?

>there might be another effect. If this is the thread stack (is it?), then>Linux will lazy-allocate the pages mapped by it, and NPTL will cycle the>stacks (ie. instead of munmap()-ing them, they get cached). I dont>remember the exact tresholds NPTL is using for caching stacks. In any>case, the RSS of the JVM process/threads should show the exact amount of>memory allocated.

I am observing that for an application using 10 threads (using nptl on rhel3.0) the pmap for the application shows 10 chunks each of 10240. Would it be correct to assume that each such chunk corresponds to the thread's stack ? also the VSZ for the app process is in excess of 100 MB. Comparing this with the application instance on solaris, the VSZ is never in excess of 10 MB under similar conditions.

The RSS for the app is comparable on both solaris and rhel3.0. Any more details explaining this would be appreciated.